The proposed research is designed to answer a number of questions concerning the development and training of language skills in the areas of receptive vocabulary, verbal imitation, and syntax with mentally retarded and nonretarded preschool age children. The questions which need detailed analysis are: Specification of prerequisite skills to receptive vocabulary, verbal imitation and syntax acquisition; specification of the interrelationship between receptive vocabulary, verbal imitation, and syntax development, and specification of efficient training procedures for preschool age mentally retarded children in each of these areas. While other programs define as their goal the education of noninstitutionalized mentally retarded children, few programs have isolated and conducted research on skills critical for later development. As progress is made in developing effective training procedures in each of the areas of proposed research, necessary adjustments will be made in the language lattice which serves as the model for language training in the proposed project request. These adjustments will serve to refocus research efforts and data gathering procedures in order to systematically improve the effectiveness and efficiency of existing language training programs for the mentally retarded.